The invention relates to a wheel axle height adjusting mechanism for attachment to a machine housing, such as for example a lawnmower housing. Typically, such lawnmowers have a housing with a top wall and side walls projecting downwardly from the top wall, and also have a motor on the housing and rotatably attached by a vertical power shaft to a rotary blade, the latter being positioned beneath the top wall and in close proximity to the ground to enable grass cutting. By adjusting the wheel axle relative to the housing, changes in the position of the blade relative to the ground are effected. Upward relative movement of the axle brings the blade closer to the ground and permits cutting the grass to a shorter length, and downward relative movement of the axle has the opposite effect.
Wheel axle height adjusters are known in various forms, but have one or more problems making them unsuitable for use in certain applications. For example, the disclosure of U.S. Pat. No. 2,836,430, issued to Laugenbacker on May 27, 1958, whose wheel height adjuster includes a contacting surface or finger engageable on one of several notches or detents, states that the position of the housing relative to the ground is adjusted from a lower position to a higher position by placing a foot on the mower's wheel and lifting the housing, whereupon the contacting surface rides out of one notch and towards another. Grasping the mower housing, particularly the lower portion of a housing's side wall which is in close proximity to the potentially dangerous rotary blade, is obviously undesirable.
Other prior art wheel adjusters include those disclosed in U.S. Pat. No. 3,210,089, issued to Hoffman, et. al., on Oct. 5, 1965, and in the U.S. Pat. No. 4,006,580, issued to Kalleicher, on Feb. 8, 1977. Both disclose means by which the relative level of the wheel axle to the housing may be adjusted by grasping or pressing an element located adjacent the wheel and vertically above the top wall of the mower housing, rendering them unsuitable as wheel adjusters for various self-propelled mowers. For example, in mowers propelled by their front wheels, power from the motor is typically transmitted to a horizontal, rotatable power shaft directly above and parallel to an axis connecting the centers of the front wheels. The ends of this horizontal power shaft are located directly above the front wheels, and fixedly attached to each end of the shaft is a spur gear which is in meshing engagement with its corresponding wheel. As the horizontal power shaft is rotated by the motor, the spur gears at the end of the shaft rotate and in turn drive the front wheels. The horizontal power shaft and spur gears, being spaced above the top wall of the housing, would prevent safe and facile access to a wheel adjuster that is actuable from above that top wall and adjacent the wheel.
Other disadvantages of many existing wheel height adjusters include their lack of interchangeability. These adjusters are designed for either the left- or right-side wheels of a machine housing and cannot be used on the opposite side. This restriction on their use requires one who assembles such wheel height adjusters to a lawnmower to maintain two different parts, complicating stocking and ordering procedures. A still further disadvantage of several existing designs is the inability of the machine operator to know at a glance whether all of the wheel axles are adjusted to the same level relative to the housing. Non-uniformity of wheel axle level results in a rotary blade that is not parallel to the ground over which it rides and can cause the lawnmower to cut grass to a non-uniform height.